animation nodes - delay frame update
You don't need conditional executions to achieve this effect, what you need is a constant seed for every nth interval. For instance, if I floor divide the time by 10, the result will be zero for the first 10 frames, 1 for the next 10 frames, 2 for the next 10 frames and so on. If I used the result of the floor division as seed, the random offset will be constants for every 10 frames.



If you want the length of the intervals to be random, we may use an approach as follows. We will initialize a variable with some integer--say zero, at each execution, we will replace that variable by another random integer if some boolean is true, that boolean has some probability $P$ of being true. The value of the variable is then constant for some interval that depends on $P$ and changes if the boolean is true. The implementation may be as follow:



AN.seed if hasattr(AN, "seed") else 0


The above expression checks if AN has a variable called seed, if it has, it returns its value, if not, it restuns zero.

AN.seed = (new if y else original)


This expression sets the variable to the frame number if the boolean y is true. The boolean is true if the value of a random variable $\in [0,1]$ of a uniform distribution is less than 0.1 (meaning the probability of being true is equal to 0.1). The probable length of the intervals is inversely proportional to the probability $P$.

Now all you have to do is to use the value of that variable as seed for the random generator and everything should work as you expect it to.